Process for manufacturing gaskets



Dec.6,1938.' 4 NmGL'EsB-Y 2,139,3 4;

PROCESS FOR MANUFACTURING GASKETS Original Filed Nov. 2, 1934 UgleayaPatented Dec. 6, 1938 PATENT OFFICE PROCESS FOR MANUFACTURING GASKETSNicholas Ewing Oglesby, Troy, N. Y., assignor to Bohr-ManningCorporation, Troy, N. Y., a corporation of Massachusetts ApplicationNovember 2, 1934, Serial No. 751,235 Renewed April 1, 1938 9 Claims.

which are not used in the gaskets, may be returned to the beaters of thepaper making machine and re-used. This method results in a saving in thequantity of fiber used, and also a saving in consumption of chemicals inthe saturating bath.

It is a further object of the invention to produce, as a new article ofmanufacture, a saturated paper gasket which is characterized by theabsence of changes in shape upon changes in moisture content which mayresult from changes in the humidity of the atmosphere.

It is old in the art to make an asbestos gasket, brake lining, or clutchfacing by first cutting a blank from a sheet of asbestos and thenimpregnating the blank with a non-hygroscopicbinder. Thereafter theportions of the sheet not used are returned to the beaters of 'the sheetforming machine. Thus, the idea of pre-cutting a fibrous sheet,impregnating the out portions, and reusing the remaining portions isold, in its broadest aspects. In the past, however, it has beenimpossible to apply such method to the production of saturated papergaskets because of the fact that paper changes materially in size(expands or contracts) when saturated, whereas asbestos sheets do not.Thus, if blanks were cut from conventional gasket making paper and thensaturated, the size and shape of the blanks would change materially, dueto saturation. For instance, if a circular, ring-shaped blank were cutfrom the usual gasket making paper, and then saturated with one of theusual saturants, and

cured, the blank would be found to be elliptical in,

shape, changed in size, and commercially useless.

In accordance with the present invention, it is a possible to determineahead of time exactly what changes in size and/ or shape may be expectedin the blank when the same is subjected to saturation, and,consequently, allowance can be made for these changes, and the blank cutaccordingly, so that the final saturated article will be exactly thedesired size and shape.

Thus, substantial economies in themani1facture of saturated papergaskets can be effected, because the blanks may be cut from the sheetprior to saturation, and the portions of the sheet not used can bereturned directly to the beaters of the paper making machines. Theseeconomies extend not only to a saving in paper fibre, but also to asubstantial saving in the material used for saturating.

In the manufacture of saturated paper gaskets it has been commonpractice to make-the paper from rope, jute, wood fibre and the like, orfrom these fibres mixed with comminuted cork. Such papers have beensaturated with a solution of glue and glycerine. The glue has beentanned, and the web dried. Finally gaskets are out in various shapesfrom the dried web. Two principal disadvantages follow from such priorart methods. In the first place it is wasteful of paper fibre andsaturating materials, because as high as fifty per cent of the saturatedweb is usually wasted. Secondly, if the saturation is not very complete,a perfect seal will not be formed around the edges of the gasket.

When the conventional methods are used, it has not been found practicalto re-use the waste resulting from cutting the gaskets, because thewaste cannot be returned directly to the beaters of the paper makingmachine, but must be subjected to a cooking process to remove thesaturant. and the expense of the cooking process has increased the costof recovering the paper fibres to a point where it has not beeneconomical.

In accordance with my process, no chemicals are present in the sheetwhen the waste material is cut therefrom, and consequently none of thesaturant is lost. All of the waste paper, after cutting, is in a formthat can be returned directly to the beater without any preliminarytreatment,

so that it may be immediately disintegrated and re-run at a nominalcost.

The essentials of my process are (1) controlling and measuring theexpansion and contraction characteristics of the desired sheet of paper.

which result from saturating and impregnating the sheet with the desiredsaturating solution; (2) computing beforehand the change in dimensionwhich will result when a blank of predetermined size is saturated; (3)cutting the gasket in accordance with such computation and allowing forthe change in dimension which will result from the saturation; (4)saturating the cut blank in the desired saturant; (5) permitting theblank to expand or contract to the desired dimension, .(6) drying thecompleted gasket. types of saturants are used, a tanning or fixing stepmay be employed before the final drying. The terms saturating andimpregnating are When certain used throughout the specification andclaims in a generic sense to cover the incorporation of a suitableamount of a saturating or impregnating agent in the body of the paper,as distinguished from mere surface painting or coating.

Another important feature of the present invention is the use of specialpapers in the manufacture of saturated paper gaskets. I have found thatgasket paper as heretofore made for saturating is not suitable for myprocess, if close tolerances in the final gasket are required. Paper asused in the past for the manufacture of gaskets has the fibres orientedpredominently parallel to the length or machine direction of the paper.Such papers have a high length and relatively low cross strength. Whensaturated, fixed, and dried, such papers expand and contractpredominantly in the cross direction, the change in the length directionbeing relatively small, either on expansion or contraction. If circulargaskets arecut from such paper, they will become elliptica'l whensaturated, and will remain elliptical after drying.

Another defect of saturated gaskets made from conventional paper inaccordance with prior art processes is that they expand and contractunevenly in the two directions with changes in moisture contentresulting from changes in humidity. An important aspect of the presentinvention relates to my discovery that saturating papers having a crossstrength to length strength ratio of about 1, expand and contractapproximately equally in both directions, both in the saturatingoperation and. when exposed to varying humidities. In paper of thistype, the fibres have a random orientation, in which about equal numbersof fibres are parallel to the length and cross directions.

I have conducted numerous tests with many samples of paper of differenttypes, and I have found that, as the cross and length strengths approachequality, the cross and length expansioncontraction characteristics ofthe sheet also approach equality. Furthermore, the ratio of cross tolength dimensional change resulting from satu'ration is substantiallyequal to the ratio of cross to length dimensional change resulting fromchanges in moisture content, which may result from humidity changes.

My experiments show that, with commercial saturating paper, such as isconventionally used, the increase in cross dimension resulting fromsaturation varies from about 1% to 1 a change which is equivalent toapproximately 1 inches per 100 inches of dimension in the gasketmaterial. .On 24 inch gaskets, this would be equivalent to .36 inchalong the cross direction 01' the paper. With such paper, the change inthe length, or machine direction, is negligible, and in fact, with somepapers, there is a slight shrinkage in that direction. It is obviousthat a precut circular gasket would therefore become an ellipse aftersaturation and it would be difiicult to allow for the expansion in onedirection and the contraction or lack of change in the other direction.Even if such an allowance could be correctly made, and a circular gasketproduced, changes in dimension resulting from changes in the humidity ofthe atmosphere would always be unequal in the two directions, and itwould, therefore, be impossible to maintain the circular form of thegasket under varying conditions of humidity. The same difliculties applyto any desired regular shape of gasket, and the circular form is used inthis specification merely as a convenient illustration.

For close tolerances a paper stock is desired which has substantiallythe same properties in both length and cross directions. Such a papermay be made on a hand sheet machine, and the fibres may be so laid downthat they have a substantially equal resultant orientation in alldirections. For certain special uses, but not for gaskets, papers ofthis type have been made with a special cross-flow vat. With these newand special machines, such as a Sonbert machine of the general typeshown in United States Patent No. 1,924,154, it is possible to obtainapproximately the same tensile strength in the length and crossdirections of the paper, or, in fact, in all directions. As statedabove, I have found that a paper with these characteristics expands andcontracts substantially the same in all directions when subjected tosaturation with the solutions disclosed below, and also when exposed tovariable conditions of humidity, and that such paper is, therefore,highly satisfactory for my process. This is true whether the paper ismade from rope, jute, wood, or a mixture of these fibres, either with orwithout the addition of comminuted cork. Likewise, many other fibres maybe used.

When a properly balanced sheet is made on a special machine so as togive a cross to length strength ratio of about 1 to 1', itis found thatthe cross strength is appreciably stronger than the cross strength ofregular papers heretofore used and that the length strength is lowerthan the length strength of regular paper as used in the past. In thecase of gaskets, however, the requirement for strength is the same inall directions and the gasket is, on the whole, no stronger than itsweakest portion. For this reason, a gasket with equal strengths in alldirections is preferred to the ordinary gasket.

.Not only is there an advantage in the overall strength in using specialpaper for my process, but when the gaskets are first cut and thensaturated, the edges of the gasket are more completely filled andsaturated, which minimizes the chance of leakage, especially since inmany cases, the paper has not heretofore been completely filled with thesaturating material.

The following is an illustration of the way in which my invention may becarried out: A roll of saturating gasket paper of the thickness requiredto produce the desired gauge of gasket, is first tested for itsexpansion characteristics when saturated. As an example, we will take apaper with a cross to length tensile strength'ratio of roughly, 1 to 1.Out of this paper, a circle or disc 24 inches in diameter is out. Pencillines are drawn on two diameters,-one-parallel and one perpendicular tothe machine direction. This circle is saturated with the impregnatingsolution by first floatingon the solution until the solution penetratesthrough and then submerging, removing from the solution and scraping theexcess solution from the surfaces by the sharp straight edge of a steelbar, A suitable saturating solution is bone glue (32 millipoises) 1part, glycerine 3 parts and water 7 parts, and a suitable temperature is130 F. The saturated circle is cooled or allowed to cool until jellingtakes place after which it is submerged in a solution of 1 partcommercial formaldehyde to 9 parts water at a temperature of 40 F.,removed, allowed to dry or dried slowly and brought to equilibrium caseof paper as indicated, the two diameters will have increasedsubstantially the same, for example, .12" or .5%. Assuming that it isdesired to cuta circular gasket 20 in outside diameter with a 1" face,i. e., 18-" inside diameter, we will pre-cut from the paper an outsidediameter of X:

or 100.5X=2000 The inside diameter will be Y:

x or 100.5Y=1800 In this case, the raw paper stock is cut into circularpaper rings of 19.90" outside diameter and 17.91" inside diameter.

The rings so cut from the raw paper stock are next saturated, scraped,cooled, and cured in substantially the manner described above withreference to the disc, using substantially the same solution.

The operations may be carried out by hand as described for the testcircle of paper, or the operation may be carried out continuously onsuitable equipment. For instance, it has been found very satisfactory topractieethe method of my invention, by using a machine such as the oneshown diagrammatically in the accompanying drawing, although many othertypes of machines may be employed with equal success.

In the accompanying drawing:

Figure l is a diagrammatic vertical sectional view of a portion of amachine adapted to carry out my process;

Figure 2 is a similar view of another portion of the apparatus, and

Figure 3 is a similar view of still another portion of the apparatus.

Referring to Figure 1, a plurality. of rolls 5 are shown carrying aflexible wire belt 6 through a tank 1 containing a solution 8 which mayconsist of the ingredients mentioned'above, namely,

-a refrigerating chamber submersion, if this method of operation is-preferred for any particular type of gasket. From the wire belt 6,gaskets are dumped upon a cloth belt II which is carried by rolls l2through rubber calender rolls l3, where the excess of the impregnatingsolution is squeezed from the surface of the gaskets ill. Such solutionflows into the box l4, from which it may be pumped or otherwise conveyedback to the tank I. From the belt II, and after passing through thecalender rolls I3, the gaskets are dumped onto a second wire belt 15,carried by rolls l6.

Referring to Figure 2 the belt I5 is a continuation of that shown inFigure l, and in addition to the rolls E6, the belt is supported by athird roll H. The gaskets, after being dumped from the belt ID to thebelt l5, are carried thereby through 18, the latter being cooled by anysuitable commercial refrigerator installation. A desirable temperaturerange within the refrigerator I8 is between 34 and 38 F., a temperature.low enough to cool but not low enough to freeze the water in thesaturating solution contained in the gaskets l0. From the belt I5 thegaskets are dumped upon another flexible wire belt l9 carried by rolls20 and passed under idler rolls 2|, and the gaskets are fixed by thesolution 22 in the tank 23. A suitable fixing solution is 1 partcommercial formaldehyde to 9 parts of water and a suitable temperatureis 40 F. From the flexible wire belt IS, the gaskets are dumped upon athird belt 24, a fragmentary portion of which is shown in Figure 2.

Referring to Figure 3, the gaskets are dumped upon the belt 24 carriedby rolls 25, and the belt extends into a drying chamber 26. At the endof the travel of belt 24, the gaskets are dropped upon another belt 21within the drying chamber, trained about rolls 2B. The gaskets areconveyed by the last-mentioned belt lengthwise of the drying chamber andoutwardly therefrom. They may be deposited into any suitable container29 after their complete travel through the drying chamber. The chamber26 should be kept at a suitable temperature, preferably not in excess of90 F., a good range being between and Many well known methods of heatingthe chamber may be used, but it is preferred to circulate heated airtherethrough, discarding part of the circulated air and adding new warmair to keep the humidity range between '30 to 40%. The humidity rangemay, however, be varied within wide limits, depending upon the rate ofdrying desired.

In the past both cylinder and Fourdrinier papers have been used forsaturation to form gaskets. As a general proposition, the cross tolength tensile strength ratio of Fourdrinier paper has been higher thanthat of cylinder paper. That this was true was purely an accidentaldifference of the two types of paper making machines. While the ratiohas been somewhat more favorable with Fourdrinier machines, cylindermachines have been more extensively used, since the cylinder type papermachines form gasket material with h gher tensile strengths and since itis easier to make the thicker gauges of matetion is relatively less withthethicker gauges, since V combing is an action occurring primarily atthe surface just after the fibres are deposited. Likewise the cylindersare run at lower speeds in making the thicker gauges and this alsoreduces the combing action. In no case of either cylinder or Fourdrinierpaper has the cross to length tensile strength ratio exceeded .80 and ithas only been on rare occasions that either the thicker gauges ofcylinder paper or the Fourdrinier papers had a cross to length tensilestrength ratio as high as .65. Since this condition has existed in theprior art it follows that while some of the prior papers are much betterthan others, none of them approach the ideal condition of a cross tolength strength ratio of l to 1.

Where cross to length tensile strength ratio is used in thesespecifications, it should be understood that this ratio is obtained bydividing the cross tensile strength by the length tensile strength. Thelength direction is what is known as the machine direction. The crosstensile strength is obtained by testing 1" strips of paper cutperpendicular to the machine direction. The length tensile is obtainedby testing 1" strips which are cut parallel to the machine direction.All tests are made at a relative humidity of 65% and a temperature of 70F., after the paper has been conditioned at this humidity andtemperature for at least two hours. A paper testing machine, motordriven, such as a Scott machine, is used. At least three samples areused for each determination. The testing machine is motor driven. Thedistance between jaws of the testing machine is 5", and the speed oftravel of the testing machine is from '7 to 8 inches per minute. Samplesthat break in the jaws of the testing machine should be rejected.Results used as cross and length tensile strengths, respectively, arethe average of three tests in each case.

It should also be understood that where the term cylinder paper is used,the paper may be -formed on one cylinder to produce a one ply cylinderpaper, or on two or more cylinders to produce a multiple ply cylinderpaper.

I claim:

1. The process of making gaskets of predetermined size and shape frompaperlike material including cellulosic fibres in amount which willcause the paper to change dimensions upon saturation, comprisingdetermining the dimensional change characteristics of the paperlikematerial upon saturation with a binder solution which swells cellulose,forming a blank from said paperlike material having a dimensional areaand shape such that after saturation with such a binder and bringing toequilibrium with average atmospheric conditions the gasket will assume adesired size and shape, saturating the said blank with such a binder andcausing expansion of the cellulosic fibres and change in the dimensionalarea of the formed blank and whereby the body portion and edges of theblank are saturated, and bringing the saturated gasket to conditions ofequilibrium with average atmospheric conditions.

2. The process of making gaskets of predetermined size and shape frompaperlike material including cellulosic fibres in amount which willcause the paper to change dimensions upon saturation, comprisingdetermining the dimensional change characteristics of the paperlikematerial upon saturation with an aqueous binder solution, iorming ablank from said paperlike material having a dimensional area and shapesuch that after saturation with said binder and drying, the gasket willassume a desired size and shape, saturating the said blank with saidbinder and causing expansion of the cellulosic fibres and change in thedimensional area of the formed blank and whereby the body portion andedges of the blank are saturated, and drying the saturated gasket.

3. The process of making gaskets of predetermined size and shape frompaperlike material including cellulosic fibres in amount which willcause the paper to change dimensions upon saturation, comprisingdetermining the dimensional change characteristics of the paperlikematerial upon saturation with a glutinous binder solution which swellscellulose, forming a blank from said paperlike material having adimensional area and shape such that after saturation with said binderand bringing to equilibrium with average atmospheric conditions, thegasket will assume a desired size and shape, saturating the said blankwith said binder and causing expansion of the cellulosic ,fibres andchange in the dimensional area of the formed blank and whereby the bodyportion and edges of the blank are saturated, and bringing the saturatedgasket to conditions of equilibrium with average atmospheric conditions.

4. The process of making gaskets of predetermined size and shape frompaperlike material including cellulosic fibres in amount which willcause the paper to change dimensions upon saturation, comprisingdetermining the dimensional change characteristics of the paperlikematerial upon saturation with a binder of glue and glycerine whichswells cellulose, forming a blank from said paperlike material having adimensional area and shape such that after saturation with said binderand bringing to equilibrium with average atmospheric conditions, thegasket will assume a desired size and shape, saturating the said blankwith said binder and causing expansion of the cellulosic fibres andchange in the dimensional area of the formed blank and whereby the bodyportion and edges of the blank are saturated, and bringing the saturatedgasket to conditions of equilibrium with average atmospheric conditions.

5. The process of .making gaskets of predetermined size and shape frompaperlike material including cellulosic fibres in amount which willcause the paper to change dimensions upon saturation, comprisingdetermining the dimensional change characteristics of the paperlikematerial upon saturation with a binder of glue, glycerine and waterwhich swells cellulose, forming a blank from said paperlike materialhaving a dimensional area and shape such that after saturation with saidbinder and bringing to equilibrium with average atmospheric conditions,the gasket will assume a desired size and shape, saturating the saidblank with said binder and causing expansion of the cellulosic fibresand change in the dimensional area of the formed blank and whereby thebody portion and edges or the blank are saturated, and bringing thesaturated gasket to conditions of equilibrium with average atmosphericconditions.

6. The process of making gaskets of predetermined size and shape frompaperlike material including cellulosic fibres in amount which willcause the paper to change dimensions upon saturation, comprisingdetermining the dimensional change characteristics of the paperlikematerial upon saturation with a binder solution which swells cellulose,cutting a blank from said paperlike material having a dimensional areaand shape such that after saturation with said binder and bringing toequilibrium with average atmospheric conditions, the gasket will assumea desired size and shape, saturating the pre-cut blank with said binderand causing expansion of the cellulosic fibres and change in thedimensional. area of the formed blank and whereby the body portion andedges of the blank are saturated, and bringing the saturated gasket toconditions of equilibrium with average atmospheric conditions.

7. The process of making gaskets of predetermined size and shape frompaperlike material having a cross to length strength ratio of 0.80 to 1and including cellulosic fibres in amount which will cause the paper tochange dimensions upon saturation with a binder solution which swellscellulose, comprising forming a blank from said paperlike materialhaving a dimensional 76 area and shape such that after saturation withsuch a binder, the saturated gasket will have substantially the sameshape as the blank but will be of a different size, saturating the blankwith such a binder and causing expansion of the cellulosic fibres andchange in the size of the formed blank, and whereby the body portion andedges of the blank are saturated, and bringing the saturated gasket toconditions of equilibrium with average atmospheric conditions.

8. The process of making gaskets of predetermined size and shape frompaperlike material including cellulosic fibres in amount which willcause the paper to change dimensions upon saturation, comprisingdetermining the dimensional change characteristics of the paperlikematerial upon saturation with a binder solution which changes thedimensions of the material, forming a blank from said paperlike materialhaving a dimensional area and shape such that after saturation with sucha binder and bringing to equilibrium with average atmospheric conditionsthe gasket will assume a desired size and shape, saturating the saidblank with such a binder and causing change in the dimensional area ofthe formed blank and whereby the body portion and edges of the blank aresaturated, and bringing the saturated gasket to conditions ofequilibrium with average atmospheric conditions.

9. The process of making gaskets of predetermined size and shape frompaperlike material including cellulosic fibres in amount which willcause the paper to change dimensions upon saturation, comprisingdetermining the dimensional change characteristics of the paperlikematerial upon saturation with a binder solution which shrinks thematerial, forming a blank from said paperlike material having adimensional area and shape such that after saturation with such a binderand bringing to equilibrium with average atmospheric conditions thegasket will assume a desired size and shape, saturating the said blankwith such a binder and causing shrinkage in the dimensional area ofthe'formed blank and whereby the body portion and edges of the blank aresaturated, and bringing the saturated gasket to conditions ofequilibrium with average atmospheric conditions.

NICHOLAS EWING OGLESBY.

